1. Field of the Invention
The invention relates generally to seismic shear wave generators and, more particularly, but not by way of limitation, it relates to vibrator apparatus for generating elliptically polarized shear waves in an earth medium.
2. Description of the Prior Art
Applicant knows of no prior art that deals with methods or apparatus for generating elliptically polarized shear waves or for utilization of such shear waves in any form of seismic exploration. A search of the prior art discloses that the probable closest prior art are U.S. Pat. Nos. 3,208,935 and 3,034,594, each of which provide a relatively old teaching for generation of torsional shear waves. Each of these generators teaches an apparatus for cranking or torquing a surface of earth medium to generate such torsional wave energy. Generation of such torsional wave is an attempt to induce rotary particle motion, i.e. twisting, about an axis extending in the direction of propagation. This is an entirely different form of seismic wave than the elliptically polarized shear wave.